The subject invention relates to carboxylated amide polymers. The carboxylated amide polymers are useful in coating compositions, especially aqueous coating compositions, for the coating of food and beverage containers.
Containers intended for use in the food and beverage industry typically have an interior coating applied to them. The coating is quite thin and serves the purpose of protecting the container from any adverse effects from the food or beverage as well as insuring that the food or beverage is not contaminated or given a bad taste by the container. Aluminum, steel and tin-plated steel are typically used in the construction of food and beverage containers.
Various epoxy and acrylic coating compositions have been used for the coating of food and beverage containers. Any coating must meet stringent requirements in order to be useful for this purpose. The coating must adhere well to the base metal and must possess a certain set of flexibility, extensibility and adhesion characteristics so as to withstand the processing of the container itself. The coating must also be able to resist heat which can be encountered during processing of the container. Additionally, the coating itself must not affect the taste of a food or beverage which is put into the coated container. Several solutions have been offered for meeting the aforementioned requirements. Many different compositions have met with limited success. However, there is still a need for a coating composition which is able to meet all the aforementioned requirements.
An aqueous coating composition which possesses the proper combination of properties would be most desirable. This is because of recent concerns as to the polluting effect which the organic solvents in an organic solvent based composition can have on the environment. An aqueous coating composition is free of these concerns.
There has now been found novel carboxylated amide polymers which possess many of the properties desired of a polymer intended for use in the coating of a food or beverage container. The carboxylated amide polymer can be made water reducible and thus applied from an aqueous composition.
As used herein all percentages and ratios are by weight unless otherwise indicated.